Passive Monitoring of DNS Anomalies Bojan Zdrnja1, Nevil Brownlee1, and Duane Wessels2 1 University of Auckland, New Zealand, b.zdrnja,nevil @auckland.ac.nz { } 2 The Measurement Factory, Inc.,
[email protected] Abstract. We collected DNS responses at the University of Auckland Internet gateway in an SQL database, and analyzed them to detect un- usual behaviour. Our DNS response data have included typo squatter domains, fast flux domains and domains being (ab)used by spammers. We observe that current attempts to reduce spam have greatly increased the number of A records being resolved. We also observe that the data locality of DNS requests diminishes because of domains advertised in spam. 1 Introduction The Domain Name System (DNS) service is critical for the normal functioning of almost all Internet services. Although the Internet Protocol (IP) does not need DNS for operation, users need to distinguish machines by their names so the DNS protocol is needed to resolve names to IP addresses (and vice versa). The main requirements on the DNS are scalability and availability. The DNS name space is divided into multiple zones, which are a “variable depth tree” [1]. This way, a particular DNS server is authoritative only for its (own) zone, and each organization is given a specific zone in the DNS hierarchy. A complete domain name for a node is called a Fully Qualified Domain Name (FQDN). An FQDN defines a complete path for a domain name starting on the leaf (the host name) all the way to the root of the tree. Each node in the tree has its label that defines the zone.